As stated, it's crucial that privacy be fully respected for users. The key thing may not necessarily be knowing exactly who someone is, but instead knowing what they've done (which features they use and how often, which marketing emails they open, which support tickets they file, etc) and using this to give users better experiences personalized around their history of interactions. Providing this type of experience from web companies is what we're working on at Klaviyo (<a href="http://www.klaviyo.com" rel="nofollow">http://www.klaviyo.com</a>).<p>In most cases, companies are tracking all of this data, just in multiple different systems and not bothering to pull it together (i.e. why do I get emails about product features I already use?) to use to make my life better.<p>On privacy, companies need to make sure they are being open with users. For most of these so-called "people analytics" companies can choose whether to include personally identifiable info. Companies need to be intentional, and should choose to anonymize customer data when they can (but should still treat people uniquely based on their past interactions, even if they can't put a name on someone).